Steviol glycosides are found in the leaves of Stevia rebaudiana (Bertoni) Bertoni (Compositae), and/or Rubus suavissimus S. Lee (Rosaceae) and are responsible for the sweet taste of the leaves. A number of high potency sweeteners of plant origin are known and the major 20 structural types have been reviewed, for example, by Kim and Kinghorn (2002), Arch Pharm Res 25, 725-746. One subgroup of terpene high potency sweeteners are diterpene compounds, among which the so-called “steviol glycosides”, also known as “ent-kaurene glycosides”, form another subgroup.
Steviol glycosides range in sweetness from 40 to 300 times sweeter than sucrose. However, as with many high potency sweeteners, they also provide a bitter taste and/or off-note/aftertaste, and this limits their use in consumables. Methods that are able to identify agents that are able to modulate, and in particular to inhibit or mask, this bitter taste/aftertaste of steviol glycosides are therefore of interest.
Bitter taste is perceived via taste receptors, and a family of at least 25 functional bitter taste receptors (TAS2R or T2R) is known. Extensive deorphanization work has been done and many ligands have been published. However, none of these receptors has previously been shown to be activated by steviol glycosides.